The invention generally relates to a cleaning composition and process for removal of photoresist residue from semiconductor device substrates after plasma etching and ashing processes in the fabrication of integrated circuits.
Numerous steps are involved in the fabrication of microelectronic structures. Within the manufacturing scheme of fabricating integrated circuits, selective etching of different surfaces of the semiconductor is sometimes required. Historically, a number of vastly different types of etching processes, to selectively remove material, have been successfully utilized to varying degrees. Moreover, the selective etching of different layers, within the microelectronic structure, is considered an important step in the integrated circuit fabrication process.
In the manufacture of semiconductors and semiconductor microcircuits, it is frequently necessary to coat substrate materials with a polymeric organic substance. Examples of some substrate materials includes aluminum, titanium, copper, silicon dioxide coated silicon wafer, optionally having metallic elements of aluminum, titanium, or copper, and the like. Typically, the polymeric organic substance is a photoresist material. This is a material which will form an etch mask upon development after exposure to light.
In subsequent processing steps, at least a portion of the photoresist is removed from the surface of the substrate. One common method of removing photoresist from a substrate is by wet chemical means. The wet chemical compositions formulated to remove the photoresist from the substrate should do so without damaging the substrate (e.g., corroding, dissolving, and/or dulling the surface of any metallic circuitry of the substrate; chemically altering the inorganic substrate; and/or attacking the substrate).
Another method of removing photoresist is by a dry ash method where the photoresist is removed by plasma ashing using either oxygen or forming gas such as hydrogen. The residues or byproducts may be the photoresist itself or a combination of the photoresist, underlying substrate and/or etch gases. These residues or byproducts are often referred to as sidewall polymers, veils or fences.
Increasingly, reactive ion etching (RIE), is the process of choice for pattern transfer during via, metal line and trench formation. The RIE process typically leaves a residue or a complex mixture that may include re-sputtered oxide material, organic materials from photoresist, and/or antireflective coating materials used to lithographically define the vias, metal lines and or trench structures.
The prior art teaches a variety of cleaning compositions designed to remove residues and byproducts that result from semiconductor manufacturing processes. However, compositions that were once suitable for cleaning state of the art semiconductor materials are not as suitable for use with more recently developed materials, such as organosilica glass (OSG) dielectrics and other low-k dielectrics.
For example, U.S. Pat. No. 5,698,503 (Ward et al.), U.S. Pat. No. 5,792,274 (Tanabe et al.), U.S. Pat. No. 5,905,063 (Tanabe et al.), U.S. Pat. No. 5,962,385 (Maruyama et al.), U.S. Pat. No. 6,235,693 (Cheng et al.), U.S. Pat. No. 6,248,704 (Small et al.), U.S. Pat. No. 6,638,899 (Wakiya et al.), U.S. Pat. No. 6,677,286 (Rovito et al.), U.S. Pat. No. 6,773,873 (Seijo et al.), U.S. Pat. No. 6,821,352 (Rovito et al.) and U.S. Pat. No. 6,828,289 (Peters et al.), and U.S. Pat. App. Pub. No. 2004/0016904 (Baum et al.) disclose cleaning compositions comprising organic solvents. Organic solvents can be unsuitable for use with certain low-k dielectrics if they react with the organic and hydrogen substituents to produce a chemically altered dielectric material.
U.S. Pat. No. 6,197,733 discloses a cleaning composition comprising water, an ammonium fluoride compound, and an amphoteric surfactant of which the cationic group is an ammonium salt and of which the anionic group is a carboxylate. The patent is silent regarding the pH of the composition.
The pH of cleaning compositions is an important factor in their effectiveness in removing residues, etc. and in their compatability with substrates being cleaned. In the presence of highly acidic or alkaline aqueous formulations, the Si—O and Si—H bonds of low-k dielectrics can be converted to OH groups, thereby increasing the dielectric of the low-k dielectric. Moreover, highly acidic cleaning compositions containing hydrofluoric acid are not particularly suitable for use with aluminum, aluminum alloys containing copper, copper or carbon-doped oxide. It has therefore been proposed to use buffering agents in cleaning compositions to maintain the pH within a desired range.
For example, U.S. Pat. App. Pub. No. 2004/0266637 (Rovito et al.) discloses aqueous, buffered, fluoride containing compositions having a pH of greater than 7.0 to about 11.0. Buffered compositions are said to have an extended worklife because pH dependent attributes such as oxide and metal etch rates are stable so long as the pH remains stable.
U.S. patent application Ser. No. 11/050,562, assigned to Air Products and Chemicals, Inc., discloses a cleaning composition and method composition for removing residue wherein the composition has a pH ranging from about 2 to about 9, and the composition comprises: a buffer solution comprising an organic acid and a conjugate base of the organic acid in a molar ratio of acid to base ranging from 10:1 to 1:10; a fluoride, and water, provided that the composition is substantially free of an added organic solvent.
Despite the foregoing developments, it is desired to provide a selective cleaning composition and process capable of removing residues such as, for example, remaining photoresist and/or processing residues, such as for example, residues resulting from selective etching and/or ashing. Moreover, it is desired to provide a selective cleaning composition and process, capable of removing residues such as photoresist and/or post-etching/ashing residue, that exhibit high selectivity for the residue as compared to metals, high dielectric constant materials (referred to herein as “high-k” dielectrics), silicon, silicide and/or interlevel dielectric materials including low dielectric constant materials (referred to herein as “low-k” dielectrics), such as deposited oxides that might also be exposed to the cleaning composition. It is also desired to provide a composition that is compatible with and can be used with such sensitive low-k films as HSQ, MSQ, FOx, black diamond and TEOS (tetraethylsilicate).
All references cited herein are incorporated herein by reference in their entireties.